GSoC Week 3

This week was focused on changing the behaviour of Pow and exp leading term methods to raise PoleError when the argument of the function is unbounded.

Previously, they returned the original function itself for compatibility reasons, however, this isn’t accurate as no power series expansion exists. By the docstring of leadterm, it returns (c, e) where c*x**e is the first term of the power series expansion.

This change caused much of the limit and series code to break, and required addition of try-except statements to handle the exception.

Along with these two functions, factorial and gamma also saw similar changes. With this, PR#21589 is ready for review.

Next week will be focused on addressing the review comments and then proceeding to add _eval_nseries and _eval_as_leading_term methods for other special functions.